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Holtzauge

WW1 airplane handling characteristics: An interview with Swedish aviator Mikael Carlson

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Posted (edited)

I recently had the good fortune to interview Mikael Carlson about what it is like to fly his Fokker Dr.1. My initial intention was to include this text in a revised version of a paper I have put together on the Sopwith Camel’s and Fokker Dr.1’s relative turn performance but since the result was pure gold I asked and received Mikael’s consent to post it here as well.

 

Mikael has taken pains to build what is arguably a carbon copy of a Fokker Dr.1 accurate down to the last nuts and bolts. Not only that, but he flies it in advanced manoeuvres as well meaning he is in a unique position to talk about the Dr.1’s flying characteristics since this is not a replica but an actual reincarnation of the plane built and flown as it was in WW1.

 

Mikael’s Dr.1 is also authentic in terms of instrumentation meaning there are no hard numbers on stall and maximum speed available since he flies the plane as it was flown back in WW1, i.e. by feel. Concerning turns, while Mikael says he has not timed them, there is no marked difference in turn times left or right once settled into the turn but the gyroscopic forces do help in establishing a turn to the right while opposing a turn to the left. He also confirmed that the Dr.1 slows down rather quickly in tight turns, just as predicted in my C++ computer simulations.

 

Contrary to common belief, the gyroscopic effect in the Dr.1 is quite manageable and gyroscopic forces are in fact more pronounced in a P-51 according to Mikael who not only flies the Mustang but also the Hangar10 operated Bf 109G-6 putting him in an authoritative position to judge these airplanes relative handling characteristics. Interestingly, another airplane he has flown that exhibits pronounced gyroscopic effects is not a rotary powered plane but surprisingly enough the jet powered de Havilland Vampire with its huge radial compressor. Returning to the Dr.1’s gyroscopic precession characteristics, he said these are quite manageable unless at very low speeds close to stall and that consequently, he tends to lean a loop slightly to one side in order to have control of in which direction the Dr.1 departs should the speed become too low at the top of a loop.

 

The Dr.1’s stall characteristics are very benign according to Mikael and in fact the aircraft does not have a pronounced stall point but kind of mushes when exceeding the stall angle of attack while still retaining good control authority which supports the popular legend that Fokker’s thick winged Göttingen profiled Fokker Dr.1 and D.VII had the ability to hang by the propeller to catch an unwary Entente pilot from below.

 

In yaw the Dr.1 is neutral in directional stability meaning that if the pilot uses rudder to give the plane a certain yaw angle, it will stay there until the pilot actively uses the rudder again to bring it back on track lending credence to the Dr.1’s purported ability to fly sideways while firing its guns.

 

When asked about the Dr.1’s spin characteristics, Mikael said he has chosen not to explore this part of the flight envelope since the high rotational speeds in a spin would cause significant gyroscopic precession loads on the bearings of the engine which seems like a prudent precaution given how scarce and valuable the remaining original WW1-era rotary engines are.

 

A further note of interest is that he said that the aerodynamic overhang balances on the Dr.1’s control surfaces work well and there is no tendency for overbalance within the flight envelope and the aileron stick forces remain light allowing rolling manoeuvres even at higher speeds which is in stark contrast to the aerodynamically unbalanced ailerons on the Pfalz D.VIII which he says are hard to budge at higher speeds. Regarding the Fokker D.VII, he said that this airplane has the same pleasant and well balanced control characteristics as the Dr.1 and in addition has such benign flying characteristics that he likened it to a Piper Cub.

 

Another interesting point regarding aerodynamic characteristics that both the Dr.1 and D.VIII have in common is that they are tail heavy: Given Mikael’s quest for historic accuracy, both planes have been balanced as they flew in WW1 and the center of gravity is as far back as 32 % MAC which explains the significant down elevator needed on the Dr.1 to keep the nose down. In fact, he has equipped his Dr.1 with a bungee-cord connected to the stick so that there is some level of trimming available to handle the stick forces needed to maintain the pronounced stick forward position needed to keep in level flight. With the center of gravity so far back he points out, the aircraft is basically unstable in pitch and needs to be flown preemptively at all times.

 

Taxiing is best done with helpers on the wings assisting in getting the aircraft in the right direction and lined up for take-of. There is however directional control available should it be needed, if the skid is unloaded and the engine gunned to get sufficient airflow over the rudder. Landing the Dr.1 should always be done as close to a three point landing as possible and into the wind using the elevator to push the tail down and get traction for the skid after touchdown. Crosswinds are to be avoided as far as possible and the plane is prone to ground looping and after touchdown some engine power and constant attention with the rudder is needed to maintain course. Attempting wheeler landings is off the table as it is an open invitation for a ground loop and consequently something he avoids doing in the Dr.1.

 

As a final note on handling characteristics, Mikael commented that pilots sometimes like to tell stories and that the Dr.1 is in fact not that difficult to fly as long as you have sufficient experience flying it. Different in the sense that other combinations of control movement are needed but as long as you are familiar with the airplane and the somewhat unorthodox engine control, it is not that much more difficult to handle than a more conventional plane. That however said with the caveat that the Fokker Dr.1 does require the pilot to handle it in the correct way and pay constant attention or, as he puts it, it will turn right back and bite you.

 

 

I had the opportunity to take some photos as well and below is a picture of one very happy camper (me) in front of Mikael’s Fokker D.VII taken last weekend.

Me and Fokker DVII 200801.gif

Edited by Holtzauge
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Posted (edited)

Glad you like it! I can tell you it was just great being there and Mikael is like a walking encyclopedia: He knows these aircraft down to the minutest detail and I learned a lot during my visit.

Edited by Holtzauge

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21 minutes ago, Holtzauge said:

In fact, he has equipped his Dr.1 with a bungee-cord connected to the stick so that there is some level of trimming available to handle the stick forces needed to maintain the pronounced stick forward position needed to keep in level flight.

 

Thanks for sharing! I'm hoping we can have this bungee cord option in the game (ie the old response curve for horizontal stabilizor)!

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I will post a link to a Pfalz D.VIII cockpit walkaround video later where you can see the arrangement. As far as I can tell that is the only detail that differs this from a WW1 example and it looks pretty easy to disconnect if you want a "realistic" FM. ;)

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Posted (edited)

(edited to delete my response about how gamey I think RoF calibration offsets are!  🙂)

 

@Holtzauge  Cool information.  I'm surprised to learn the Dr.I will hold a crab angle like you describe.  I had always heard the Dr.I had a unique ability to do flat rudder turns, with the controls crossed, which I take to mean that they would put in the rudder, hold the wings level with opposite aileron, and instead of holding a crab, it would basically turn around like a car on a road, very rapidly.  Maybe I'm misuderstanding what that was.

Edited by SeaSerpent

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Posted (edited)

Yep, apparently the Dr.1 can do that and when I asked him what airplane he preferred he actually said the Dr.1 over the D.VII which kind of surprised me since the D.VII has so much more performance but apparently the manouverability of the Dr.1 is so amazing at low speeds that he would take it anyway. Puts MvR fondness for the Dr.1 in a whole new light IMHO.

 

13 hours ago, US63_SpadLivesMatter said:

My lord that D7 is beautiful.

 

Wait for it: DVII video incoming!

 

Link to video.

Edited by Holtzauge

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3 hours ago, Holtzauge said:

Fokker Dr.1  had the ability to hang by the propeller to catch an unwary Entente pilot from below.

 

I rather wondered about that.  I am led to believe that when stalled, or on the verge of a stall, such as at touch down, the middle wing blanks, to a certain extent, the rear control surfaces, so prop hanging, while possible was maybe not the be all and end all.

3 hours ago, Holtzauge said:

the center of gravity is as far back as 32 % MAC which explains the significant down elevator needed on the Dr.1 to keep the nose down

So what's the aircraft like to dive ?  Maybe it didn't go fast enough in a dive to overpower, what was left of the elevator downward travel ?

3 hours ago, Holtzauge said:

He also confirmed that the Dr.1 slows down rather quickly in tight turns

I suspect this is true of all the aircraft.  Something not really demonstrated in either RoF or FC.  I imagine the cut off between either, best climb and too much climb and best turn and too much turn is far more dramatic, or a cliff edge, than the game makes out.

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4 minutes ago, HagarTheHorrible said:

I suspect this is true of all the aircraft.  Something not really demonstrated in either RoF or FC. 

 

Well they nailed it with the SE5....

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Yesterday, my wife and I watched this video of Carlson's Dr.1 dogfighting a FVM Tummelisa.  Check it out:   

 

I've previously seen demos by Gene and Kermie, historical groups, etc. but they all fly the triplane rather sedately and I do understand why.   

 

But this video of Carlson's is the first I've seen where I felt like the pilot was actually flying the plane even close to the kinds of maneuvers occurring in air combat; or like what we find in FC1.  

 

When I compare this video to FR's of the FC1 Dr.1, the speed and maneuvering appear so similar I'm having a hard time telling them apart.  

 

In sum: I think this video does a lot to confirm that the FC1 Dr.1 performance is very close to the real thing.  Sure looks that way to me on film, anyway.

 

And if you've never seen a Tummelisa before; here ya go.

 

Prosit!  

 

 

3 hours ago, Holtzauge said:

Yep, apparently the Dr.1 can do that and when I asked him what airplane he preferred he actually said the Dr.1 over the D.VII which kind of surprised me since the D.VII has so much more performance but apparently the manouverability of the Dr.1 is so amazing at low speeds that he would take it anyway. Puts MvR fondness for the Dr.1 in a whole new light IMHO.

 

 

Wait for it: DVII video incoming!

 

It's the flying rudder and lack of a vertical stabilizer that gives the triplane the superior ability to skid and slip in comparison to planes that do have vertical stabs.

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8 hours ago, US93_Talbot said:

 

Well they nailed it with the SE5....

 

Many a true word spoken in jest.  Rightly, or wrongly, I had been thinking exactly that.

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Posted (edited)
11 hours ago, HagarTheHorrible said:

I rather wondered about that.  I am led to believe that when stalled, or on the verge of a stall, such as at touch down, the middle wing blanks, to a certain extent, the rear control surfaces, so prop hanging, while possible was maybe not the be all and end all.

So what's the aircraft like to dive ?  Maybe it didn't go fast enough in a dive to overpower, what was left of the elevator downward travel ?

I suspect this is true of all the aircraft.  Something not really demonstrated in either RoF or FC.  I imagine the cut off between either, best climb and too much climb and best turn and too much turn is far more dramatic, or a cliff edge, than the game makes out.

 

About the prophanging I think the point is that it is possible in the Dr.1, not that it solves all problems. However, it seems the Pfalz is a very different beast in this regard and while Mikael says he is just in the early phases of testing the Pfalz, he did say that his current feeling was that the thin cambered wing profile gives the Pfalz very different flight characteristics from the thick winged Dr.1 and D.VII.

 

When it comes to diving Mikael says he is limited to a ceiling of 2500 ft due to airspace restrictions over the field so difficult to test.

 

About turning characteristics, I will post a paper on that later on when I have updated it. In the meantime you can find the older version over at The Aerodrome forum. Mind you the one posted there right now is a bit dated since it is too optimistic about the Clmax on both aircraft and the propeller model on the Dr.1 needed updating and in the latest version I will post soon the Camel does retain its advantage over the major part of the envelope but the Dr.1 is now actually a shade better at really low altitudes.

Edited by Holtzauge
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Posted (edited)
14 hours ago, Todt_Von_Oben said:

It's the flying rudder and lack of a vertical stabilizer that gives the triplane the superior ability to skid and slip in comparison to planes that do have vertical stabs.

 

That Dr1 taking off, It will be the winner in this competition:

 

 

Edited by jollyjack

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